Electromagnet.



Nrrnn srans ramvr CHARLES H. RIEPL, OF CLEVELAND, OHIO, SSIGNOBVTO THE ELECTRIC CONTROLLER & 4MANUEACTURING: COMPANY, OE CLEVELAND, OHIO, A CORPORATION OF OHIO.

ELECTROMAGNET.

Application filed .T une 20, 1917.

To all whom t may concern:

mersed in oil or to electromagnets in which the magnetic pole faces or like parts are lubricated with oil.

IVhen an electromagnet immersed in oil is energized and the armature or other movable partlthereof moves into contact with the core or other stationary part of the magnet structure, the oil between the contacting parts4 is expelled and the parts come into intimate contact.

llhen the magnet is denergized, and the armature or other movable part thereof tends to move away from the stationary part, the intimacy of the contact causes the parts tov stick together for a period of time which varies according to conditions which will be mentioned hereinafter. The contact surface at which the sticking occurs may be the act-ual working magnetic pole face of the armature or core, or it may be some other relatively flat stop surface on the structure. This action is found also in magnets surrounded by air, in which the pole faces or stop surfaces are lubricated with oil.

This tendency to stick temporarily appears to be caused as follows: When the magnet is denergized and the movable part begins to move away from the stationary part, the space which forms between. the separating parts fills with oil. The rapidity with which the surfaces move apart is determined by the rapidity of the flow of oil into the space between the surfaces. If the parts tend to move apart more rapidly a vacuum forms and the movement is retarded. After the surfaces have moved apart a considerable distance, for example, an eighth of an inch, the oil surrounding the magnet can iow freely into the space between the surfaces and the movement of the parts is no longer retarded and they lmove freely to full open position.` The time period, then, during which the parts move imperceptiblv and remain-to al1 practical purposes in full closed position, and during y Specification of Letters Patent.

Patented Jan. 28, 1919.

serial no. 175,722. I

which they may be said to stick together, is determined lby the perimeter and area of the contact surfaces. The time period is directly proportional to the area of the contact surfaces, because, if the surfaces are increased, the volume of oil which must flow in between them for any given amount of movement, and, hence, the time required for it to flow, will be proportionately increased; and the time period is inversely proportional to the perimeter of the surface contact, because the larger this perimeter, the shorter the time required for a given volume of oil to flow into the space between the surfaces. It will be apparent that the greater the viscosity of the oil in any case, the longer will be the time period. If the magnet is surrounded by air, instead of by oil, and if'the con-tact surfaces are lubricated with oil, the action will be similar to that described above, the presence of the oil preventing the surrounding air from iiowing into the space between the contact surfaces ata greaterrate than the viscosity of the Oil will permit.

In magnets having small contact area, the time period required for the magnet to open is negligibly small because the perimeter is relatively large with respect to the contact area. In larger magnets the ratio between the perimeter and the area is smaller and the time period required is therefore greater. In magnets having rectangular equilateral contact surfaces, the perimeter is proportional to the square root of the contact area, and in rectangular contact. areas of other shapes, the perimeter is proportional t0 even smaller roots of contact area. In large magnets the time period may be reduced sufficiently for practical purposes, or 'made negligibly small,l by div iding up the contact area into smaller areas and by providing communicating passages from the oil surrounding the magnet, whereby the surrounding oil will have access to each subdivision of the contact area.

The principal object of this invention, therefore, is to provide an electromagnet having oil-lubricated contact surfaces, in which the contact surface area is divided up into smaller areas, the perimeter of each of which communicates directly, or by a passageway, with the surrounding air or oil vor other medium, whereby the time period of opening caused by the presence of the lubricaerig on vmay be made negiigibly small.

Other objects will be apparent. Referring to the accompanying drawing, Figure 1 is a 'view artly in section and partly in elevation, o an oil-filled tank containing an electromagnetic apparatus employing my invention; Fig. 2 is a front elevation of the core or stationary 'member of y the oil-immersed` electromagnet shown in Fig. 1, and drawn to a larger scale; Flg. 3, 1s a side elevation of the magnet core shown 1n Fig. 2; Fi 4 is ar view similar to Fig. 3, partly broen away, and showing a magnet core of larger size; and Figs. 5 and 6 are views corresponding to Figs. 2 and 3, respectively, showing a modification of my invention, and drawn to a smaller scale.

Referring to Fig. 1, I have shown the apparatus container or tank 1, containing oil or other liquid 2. Immersed in the oil is the electric or other apparatus 3, comprising the frame 7, and the alternating current magnet 8. 'Ihe'magnet 8 has the stationaryU-shaped core 4 fastened to the frame 7 at 5; the energizing winding 6 on the lower leg of the core 4; `the armature' 9 pivoted to the frame 7 at 10; and, on .the upper leg of the -core 4, the dephasing ring 11 embedded in the groove 13 in the polel face 12 of the core.

The particular type of magnet and apparatus shown form no part of my invention; but in Fig. 1, I have illustrated the magnet and apparatus fully shown and described in Strattons Patent, No. 1,225,686, granted May 8, 1917.

` The operation of that part of the apparatus involving my invention may be described as follows: When lthe winding 6 is energized with alternating current, the armature 9 is attracted toward the stationary core 4, and the upper end of the armature is brought into engagement with the pole face 12 of the core, the shading ring 1l producing at this pole a continuous pull in a manner well understood. When the Winding 6 is denergized, it sometimes occurs that the oil in which the magnet 1s immersed iiows into the space between the contact surfaces of the armature 9 and the pole face 12 so slowly that the armature is not released in the normal manner, buttemporarily sticks or remains temporarily in the closed position.

Ihave found that if the contactarea between the armature and the pole face is less than a certain maximum, this sticking `or delay in opening will notoccur, or the time period thereof will be negligibly small. In order, therefore, to prevent sticking in all cases and in all sizes of magnets, I preferably provide grooves 14 in the face of the pole 9, which divide up the pole face 85 into sections. These grooves not only reduce the Contact area of any one section .to or below the area at which sticking is negligible, but also provide channels by means of which the oil surrounding the magnet may have easy access to the entire perimeter of each of the contact surface sections. `In the magnet shown in Figs. 1, 2, and 3, the groove 13, containing the ring 11, may serve as one ofthe non-stick grooves, so that only one additional non-stick groove 14 is needed. I prefer to place these grooves in the magnet face 12 in a transverse direction with respect to the edges of the laminations. In Fig. 4, which illustrates the core of a larger magnet, three grooves 14 are required in addition to the groove 13 containing the dephasing ring 11.

I have found by experiment that a magnet having'contact surfaces measuring 2%X2,

with an average smoothness of contact surface, and. with oil having :the viscosity of N o. 32 transformer oil, satisfactory results are obtained by locating the grooves 14 transversely of the laminations, as above described, and on center lines about 1- inch 4apart. I iud also that grooves of an inch deep and of an. inch wide are satisfactory.

By locating the grooves transversely with respect to the'lamination edges, and by making them of the size mentioned, it is possible to form the grooves in the individual stampings when they are stamped from sheet A metal, which obviates the necessity of cutting them in the magnet after it is assembled. It will, however, be apparent that the grooves may be of other sizes and run in other directions from those which I have shown, the essential feature of my invention vwhen carriedl out by the employment of grooves, as above described, being that the grooves are arranged to communicate between the interior of the contact surfaces and the oil surrounding the contact surfaces, whereby the oil may have easy access not only from the outside toward the center of the surfaces by way of the perimeter of the surfaces as a whole, but also from the center toward the outside of the surfaces by way ofthe additional virtual perimeter provided by the grooves.

The grooves, instead of being placed in the pole face of the stationary core, -as I have shown and described them, may be placed in the face of the movable armature; or, if it be desirable to stop the movement of the armature toward the core upon stop surfaces other than the actual pole faces of the magnet, then the grooves may be placed in such stop surfaces. f In Figs. 5 and 6 I have shown a modification of my invention, in which a channel 15 is provided, runningthrough the body of the magnet and termmatingpin an oriiice approximately at the center of that part of the contact surface inclosed by the dephasing ring l1. This magnet is approximately of the same size as that shown in Figs. 2 and 3, though drawn to a smaller scale, and it will therefore be apparent that by employing the channel 15 l have divided up the contact surface into a ring, and have increased the virtual perimeter of the surface whereby the surrounding oil will have easy access to the contact surfaces.

`Whi1e l have shown and described my invention as applied to an electromagnet immersed in oil, it will be understood that my invention is applicable in every respect to an electromagnet surrounded by air but in which the pole faces or other` relatively dat contact surfaces are lubricated with oil. Also, while l have shown and described an alternating current electromagnet, it will be apparent that my invention is applicable in every respect to direct current electromagnets.

My invention is not limited to the exact shapes, locations, directions or dimensions of the grooves or channels which l have disclosed, and many changes and modifications other than those shown or mentioned above may be made without departing from the spirit of my invention.

l claiml. A pair of wet smooth surfaces adapted to be brought into mutual contact one of them being divided into sections by one or more channels communicating with a iiluid whereby the time required to separate said surfaces is sensibly reduced.

2. ln an electromagnet, an energizing winding, two relatively movable members adapted to be moved into contact with each other on certain wet smooth contact surfaces when the magnet is energized, one of the surfaces being divided into sections by one or more channels communicating with a surrounding fluid medium whereby the time required to separate the said members is sensibly reduced.

3. ln an electromagnet, a magnetic circuit, an energizing winding therefor, a stationary and a movable member for the circuit, wet smooth pole faces on the members, the movable member being adapted to be attracted toward the stationary member to bring the pole faces into engagement with each other when the winding is energized, and a. suiiicient number of grooves in one of the pole faces communicating with a surrounding fluid medium, whereby the time required to separate the pole faces is reduced a predetermined amount.

el. ln an electromagnet, an energizing winding, two relatively movable members adapted to be moved into cont-act with each other on certain wet smooth contact surfaces when the magnet is energized, and a s uficient number of channels communicating with one of the surfaces and with a surrounding uid medium, whereby the time required t separate the said members is sensibly reduced.

5. An oil container', a switch having mutually engageable smooth surfaces in the pil, and one or more channels communicating with one of the surfaces and the oil and dividing the same into suiiciently small areas to reduce the timeJ required to separate the surfaces a predetermined amount.

Signed at Cleveland, Ohio, this th day of June, 1917.

CHARLES H. RIPPL. 

